1. Field of the Invention
The present invention relates to thyristors and more particularly to thyristors with an ability to quench load current.
2. The Prior Art
In the past, thyristor designs have been proposed incorporating controllable emitter short circuits designed as MIS structures, either of the depletion type or the enhancement type. Before ignition of the thyristor, one MIS structure serves as a stabilization short circuit, and is switched off during triggering operation by means of a voltage pulse of a first polarity supplied to its gate, whereas another MIS structure serves as a quenching short circuit and is only switched on for the purpose of quenching the thyristor, by means of a voltage pulse of a second polarity supplied to its gate. Such MIS structures may be formed as a depletion type for one purpose and an enhancement type for the other, or alternatively, both MIS structures may be of the depletion or enhancement type. In this case the gate of one MIS structure is wired to a bias voltage which builds up a semiconductor channel below the gate or eliminates the semiconductor channel existing for a voltage-free condition of the gate; so that stabilization (or quenching) short circuits are formed. The other MIS structure is not wired to such a bias voltage so that it can perform a quenching (stabilization) short circuit function. U.S. Pat. No. 3,243,669 describes thyristors with controllable emitter short circuits designed as MIS structures, which are switched on for the purpose of a rapid quenching of the thyristors. The German Pat. No. 26 25 917 discloses a thyristor in which emitter short circuits are switched on during the occurrence of an ignition current pulse in order to prevent an ignition. Previous designs do not incorporate however a common disposition of at least one controllable emitter short circuit which serves only as a stabilization short circuit, and at least one other controllable emitter short circuit which serves only as a quenching circuit for a thyristor.